The work will be directed to three areas: 1) Defining the significance of ventricular premature beats (VPB), with specific projects determining the occurrence of VPBs as related to magnitude of risk factors for coronary heart disease, different forms of coronary disease, and mitral valvular disease as well as relating the temporal occurrence of VPBs to various events of daily life; 2) Improving methods of VPB exposure and data reduction; and 3) Determining the value of acute antiarrhythmic drug testing as a method for determining efficacy of a program for suppressing advanced grades of ventricular arrhythmia. BIBLIOGRAPHIC REFERENCES: Lown B., Temte J.V., Reich P., Gaughan C., Regestein R., and Hai H.: The basis for recurring ventricular fibrillation (VF) in the absence of coronary heart disease and its management. New Eng. J. Med. 294: 623-629, 1976. Lown B. and Buck L.: Treatment of angina pectoris. In: Current Therapy, edited by H.F. Conn, W.B. Saunder Co., Philadelphia, pp. 171-175, 1976.